Ultraviolet index

The sun is the source of life on the planet. Its rays provide us with much needed light and heat. However, ultraviolet radiation from the sun is harmful to all living things. To find a balance between beneficial and harmful effects of the sun, meteorologists estimate the ultraviolet index that reflects the degree of its danger.

Types of ultraviolet radiation from the sun

Ultraviolet radiation from the sun has a range of wavelengths and is divided into three types, two of which reach the Earth’s surface.

UVA. Long-wave radiation covering the range from 315 to 400 nm

The rays almost freely pass through all atmospheric ‘barriers’ and reach the Earth’s surface.

UVB. Medium-wave radiation covering the range from 280 to 315 nm

90% of the rays are absorbed by the ozone layer, carbon dioxide and water vapor.

UVC. Short-wave radiation covering the range from 100 to 280 nm

The most dangerous type. It is completely absorbed by stratospheric ozone before reaching the Earth’s surface.

The more ozone, clouds and aerosols the atmosphere has, the less harmful the sun’s effects are. However, those saving factors have a high natural variability. Stratospheric ozone exhibits seasonality with maximum in spring and minimum in autumn. Cloudiness is one of the most unstable weather characteristics. Carbon dioxide levels also change over time.

What UV index is dangerous?

The UV index shows the amount of UV radiation expected to reach the Earth’s surface. The UV index ranges on a scale of 0 (Low) to 11+ (Extreme).

0 – 2Low

3 – 5Moderate

6 – 7High

8 – 10Very high

11+Extreme

In mid-latitudes, the UV index reaches unsafe values (6-7) only when the sun is at its maximum elevation (late June — early July). At the equator, the UV index ranges from 9 to 11+ throughout the year.

Positive effects of ultraviolet radiation

Small amounts of UV radiation are beneficial to people, play an essential role in the production of melanin, serotonin and vitamin D, and help prevent rickets.

Melanin creates a barrier to protect the skin cells from the harmful effects of the sun. It makes our skin darker and more elastic.

What are the dangers of the sun?

When tanning, you should remember there is a fine line between beneficial and harmful UV radiation. Excessive tanning is similar to a burn. Ultraviolet radiation damages DNA in skin cells.

The protective system of the body cannot cope with such an aggressive impact. It lowers immunity, damages the retina, accelerates skin ageing and can cause cancer.

UV light destroys the DNA chain

How does the sun affect people?

Susceptibility to UV radiation depends on skin type. People of European descent are the most sensitive to the sun and need protection when the index reaches 3, while the index of 6 is considered dangerous.

At the same time, the limits for Indonesians and African-Americans stand at 6 and 8, respectively.

Who is more likely to get sun damage?

Light-skinned people

People with many moles

Children

People living in the mid-latitudes when on vacation in the south

Ice fishing enthusiasts

Skiers and climbers

People with a family history of skin cancer

In what kind of weather is the sun more dangerous?

The idea that the sun is dangerous only in hot and fine weather is a common misconception. You can get a sunburn when it’s cool or cloudy outside.

Clouds, no matter how thick, do not reduce UV radiation to zero. Clouds significantly reduce the risk of getting a sunburn in the mid-latitudes but not in traditional beach holiday destinations. For example, in the tropics, you can get a sunburn in 30 minutes if it is sunny and in a couple of hours if it is cloudy.

How to protect yourself from the sun

Follow these simple rules to protect yourself from the harmful effects of the sun:

Don’t spend much time in the sun around noon

Wear light-colored clothing and wide-brimmed hats

Wear sunscreen

Wear sunglasses

When on the beach, spend as much time in the shade as possible

How to choose sunscreen

Sunscreens have varying levels of SPF. Rated on a scale from 2 to 50+, it shows you the amount of solar radiation that breaks through the cream and reaches the skin.

For example, when applying a sunscreen with SPF 15, only 1/15, or 7% of ultraviolet rays will break through the protective film. Only 1/50, or 2% of the rays will affect the skin if you use a sunscreen with SPF 50.

Sunscreen creates a reflective layer on the skin. However, you should know that no sunscreen can reflect 100% of UV rays.

An SPF 15 sunscreen is enough for everyday use, if you spend less than half an hour in the sun. When tanning, you should opt for SPF 30 or more, while light-skinned people should use SPF 50+ sunscreen.

How to apply sunscreen

Apply enough sunscreen to cover all exposed skin, including the face, ears and neck. If you plan to stay in the sun for a long time, sunscreen should be applied twice: 30 minutes before leaving home and before hitting the beach.

The recommended amount of sunscreen is stated on the packaging.

How to apply sunscreen if you’re swimming

You should re-apply your sunscreen after swimming. Water destroys the protective film and increases the amount of ultraviolet radiation by reflecting the sun’s rays. Thus, the risk of getting a sunburn increases when you’re swimming, but you may not feel the burn due to the cooling effect of water.

Re-apply your sunscreen in case of excessive sweating and towelling.

You should remember that even the shade under an umbrella cannot fully protect you on the beach. Sand, water and even grass reflect up to 20% of UV rays, increasing their impact on the skin.